Concurrent studies on the tumor-host interactions in animals and humans with sarcomas have been undertaken. The immune response to murine sarcomas has been studied and at least two antigens have been identified on murine sarcoma cells. One of these antigens is a tumor-specific antigen and the other is a cross reactive antigen present also on murine fetal tissue. Similar studies in the human have identified an antigen on tissue cultured normal as well as sarcoma tissue that is reactive with antibodies present in the serum of sarcoma patients. Studies on the serologic dissection of human tumor antigens is in progress. Adoptive immunotherapies are being evaluated.